Research On Modeling Of Propylene Polymerization In Loop Reactor

Polypropylene industry has developed rapidly in recent years. It has become the fastestgrowing and the most active developping product of synthetic resin in the world. Propylenepolymerization is non-homogeneous distribution anion reaction, the reaction mechanism isvery complex, Moreover, there are a variety of polymerization processes, how to establish themathematical model and process simulation of polymerization reaction is the fundation ofpolypropylene process control and optimization.This thesis analyzes the propylene polymerization process and the reaction mechanismin-depth for spheriol process of HIMONT company, researches main effect factors on thepolymerization reaction rate, such as catalyst, cocatalyst, concentration of monomer,hydrogen concentration, etc. The calculation methods of reaction rate and composition densityare given.Based on material balanceand and energy balance of the polymerization process, acontinuous loop reactor steady mathematical model is established, Four-Runge-Kutta methodis used to solve the steady model. The hydrogen concentrations of acrylamide, monomerconcentration, catalyst concentration, solids holdup, reactor temperature and jacket watertemperature along the loop distribution are calculated for an industrial loop reactor.Propylene polymerization units have usually to perform switching brands to meet theneeds of the market. Control and optimization of switching process depend on dynamic modelof polymerization process. Base on materiel balance, energy balance and components changein loop reactor, a dynamic model is established to discribe polymerization process, finitetorthogonal collocation method is used to solve the mathmetic model. Dynamical responses ofsome important variables such as concentration of hydrogen, content of materials, solidsholdup, propylene monomer concentration, reactor temperature and jacket water temperatureare simulated. The effects of operating conditions on polymerization reactor are studied.Melt index is a quality index of polypropylene product. Nevertheless, it is difficult formelt index to measure on-line. The laboratory data of melt index usually update every twohours and lack real-time value for quality control of polypropylene product. Based onanalyzing the influnences of melt index, a calculation model online of melt index isdevelopped. This model can be used to quality control ofpolypropylene product.